1. Technical Field
This invention relates generally to a device and method for removing an implanted elongated structure from a patient, and more particularly, to a device and method for removing an implanted cardiac lead from a patient.
2. Background Information
A variety of medical treatments and surgical methods entail implanting an elongated structure in the body of a human or veterinary patient. Examples of such elongated structures include catheters, sheaths and cardiac electrical leads (such as pacemaker leads and defibrillator leads), and a variety of other devices. Over time, it can become necessary or desirable to remove the implanted elongated structure from the body of the patient. However, problems can be encountered in attempting removal of an elongated structure implanted in biological tissue.
For example, a heart pacemaker is typically implanted in a subcutaneous tissue pocket in the chest wall of a patient, and a pacemaker lead is positioned in the vascular system of the patient, extending from the pacemaker and through a vein into a chamber of the patient's heart. The pacemaker lead commonly includes a coiled structure such as an electrical wire coil for conducting electrical signals (such as stimulating and/or sensing signals) between the pacemaker and the heart. Defibrillator leads are generally similar and, like pacemaker leads, are located about the heart, but are affixed both internally and externally of the heart. Some leads include one or more coaxial or lateral helical wire coils having a hollow inner passageway, or lumen, that extends the entire length of the wire coil or coils. Other leads, generally referred to as “lumenless” leads, may be made with a cable or a tightly wound coil without a hollow inner passageway. In either case, the cable or wire coils are surrounded by an electrically insulating material such as a flexible tube, sheath or coating. The insulating material, generally formed of silicone or polyurethane, serves simultaneously to protect the cable and wire coils from body fluids, and in the case of bi-polar leads, to insulate the wire coils from one another.
While cardiac electrical leads typically have a useful life of many years, over time pacemaker and defibrillator leads may become encapsulated by fibrotic tissue against the heart itself or the wall of the vein, or against other surrounding tissue. Encapsulation is especially encountered in areas where the velocity of the flow of blood is low. The fibrotic tissue is tough and makes it difficult to remove the lead from the area of the heart without causing trauma to the area. For example, when small diameter veins through which a pacemaker lead passes become occluded with fibrotic tissue, separating the lead from the vein can cause severe damage, such as dissection or perforation of the vein. Furthermore, separation of the lead from the vein is usually not possible without restricting or constraining movement of the lead, i.e., fixing the lead in position with respect to the patient, and in particular, with respect to the patient's vein.
To avoid this and other possible complications, some useless pacemaker or other leads are simply left in the patient when the pacemaker or defibrillator is removed or replaced. However, such a practice can incur the risk of an undetected lead thrombosis, which can result in stroke, heart attack, or pulmonary embolism. Such a practice can also impair heart function, as the presence of plural leads can restrict the heart valves through which the leads pass.
There are many other reasons why removal of a useless lead is desirable. For example, if there are too many leads positioned in a vein, the vein can be obliterated. Multiple leads can be incompatible with one another, interfering with the pacing or defibrillating function. An inoperative lead can migrate during introduction of an adjacent second lead, and mechanically induce ventricular arrhythmia. Other potentially life-threatening complications can require the removal of the lead as well. For example, removal of an infected pacemaker lead is desirable, so as to avoid septicemia or endocarditis.
Surgical removal of a heart lead in such circumstances often involves open heart surgery, with its accompanying risks, complications and significant costs. A variety of successful methods and apparatus have been devised as alternatives to open heart surgery for heart lead removal. Several such successful methods and apparatus are described in, among others, U.S. Pat. No. 5,697,936, titled “Device for Removing an Elongated Structure Implanted in Biological Tissue,” assigned to the assignee of the present application. U.S. Pat. No. 5,697,936 is a continuation-in-part of U.S. Pat. No. 5,507,751, titled “Locally Flexible Dilator Sheath,” which was in turn a continuation-in-part of U.S. Pat. No. 5,632,749, titled “Apparatus for Removing an Elongated Structure Implanted in Biological Tissue,” which was a divisional of U.S. Pat. No. 5,207,683, titled “Apparatus for Removing an Elongated Structure Implanted in Biological Tissue;” which was a continuation-in-part of U.S. Pat. No. 4,943,289, titled “Apparatus for Removing an Elongated Structure Implanted in Biological Tissue;” which was a continuation-in-part of U.S. Pat. No. 5,011,482, titled “Apparatus for Removing an Elongated Structure Implanted in Biological Tissue;” which was a continuation-in-part of U.S. Pat. No. 5,013,310, titled “Method and Apparatus for Removing an Implanted Pacemaker Lead;” which was a continuation-in-part of U.S. Pat. No. 4,988,347, titled “Method and Apparatus for Separating a Coiled Structure from Biological Tissue.” All of the aforementioned patents describe methods and/or apparatus for removing an implanted elongated structure, and are incorporated by reference as if fully set forth herein.
Although the devices and methods described in the incorporated-by-reference patents have proven to be effective for removing elongated structures implanted in biological tissue, there is a continuing desire for improved devices for such purposes. Desirably, such improved devices will have a more compact profile than existing devices, be effective for the removal of implantable structures having a lumen as well as lumenless devices, and be structured to minimize trauma to the patient.